1. Field of the Invention
This invention relates to a vehicle safety running control system, more particularly to a vehicle safety running control system which copes with a situation in which detection of an obstacle or object present ahead of the vehicle, once detected, becomes impossible or the obstacle is lost or missed, when an automatic braking system is operated so as to avoid contact with the obstacle.
2. Description of the Related Art
Various obstacle avoidance techniques have hitherto been proposed. For example, Japanese Laid-open Patent Application Hei 6(1994)-298022 teaches detecting the distance (relative distance) of an obstacle (e.g., another vehicle running ahead on the road) relative to the vehicle with the use of a detector such as a laser radar (lidar) and alerting the vehicle driver or automatically operating (i.e., independently of the vehicle operator's brake pedal manipulation) the braking system so as to avoid contact with the obstacle.
When the laser radar is used to detect an obstacle such as another vehicle running ahead on the road and the automatic braking system is operated in response to the obstacle detection, the obstacle may sometimes be lost or missed. For example, the obstacle may be out of radar sight if the vehicle (on which the laser radar is mounted) encounters great pitching. A similar situation happens if the laser radar breaks down or fails.
On this occasion, if the automatic braking operation is immediately terminated, the vehicle driver may feel annoyance and the possibility of contact with the obstacle may increase if the obstacle is, in fact, closing near. The automatic braking operation should preferably be continued in response to the situation.
On the other hand, however, there may be a case that the detected information itself is uncertain from the reason that, for example, the detection time was short and hence, the detection accuracy was low. Moreover, the obstacle might cross quickly before the vehicle and might go away. Thus, the obstacle might be absent. If this is the case, it is not necessary to continue the automatic braking operation. The continuation of automatic braking operation would rather degrade the driving feeling or comfort.
At any rate, indiscriminate vehicle deceleration change will, if not matched to the situation, degrade the driving feeling or comfort and cause the vehicle driver to experience annoyance. Moreover, rapid vehicle deceleration change would affect the vehicle driver's maneuver.